Tritium breeding calculation in a stellarator blanket
In current blanket projects, tritium breeding ratio (TBR), the ratio of tritium production rate to the neutron production rate, is low (1.1…1.2). The MCNPX Monte-Carlo code has been used to model the neutron kinetics and to look for a principal possibility of increase TBR within a stellarator blanke...
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nasplib_isofts_kiev_ua-123456789-1945862025-02-23T17:23:16Z Tritium breeding calculation in a stellarator blanket Напрацювання тритію в стелараторному бланкеті Наработка трития в стеллараторном бланкете Chernitskiy, S.V. Moiseenko, V.E. ITER and fusion reactor aspects In current blanket projects, tritium breeding ratio (TBR), the ratio of tritium production rate to the neutron production rate, is low (1.1…1.2). The MCNPX Monte-Carlo code has been used to model the neutron kinetics and to look for a principal possibility of increase TBR within a stellarator blanket limited space. У поточних проектах коефіцієнт розмноження тритію – відношення швидкості утворення тритію до швидкості виробництва нейтронів, низький, і становить величину 1,1…1,2. Монте-карлівcький код MCNPX використовувався для моделювання нейтронної кінетики і демонстрації принципової можливості збільшення напрацювання тритію в межах обмеженого простору бланкету стеларатора. В текущих проектах коэффициент размножения трития – отношение скорости образования трития к скорости производства нейтронов, низок, и составляет величину 1,1…1,2. Монте-карловский код MCNPX использовался для моделирования нейтронной кинетики и демонстрации принципиальной возможности увеличения наработки трития в пределах ограниченного пространства бланкета стелларатора. 2019 Article Tritium breeding calculation in a stellarator blanket / S.V. Chernitskiy, V.E. Moiseenko // Problems of atomic science and technology. — 2019. — № 1. — С. 49-52. — Бібліогр.: 7 назв. — англ. 1562-6016 PACS: 52.55.Hc https://nasplib.isofts.kiev.ua/handle/123456789/194586 en Вопросы атомной науки и техники application/pdf Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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ITER and fusion reactor aspects ITER and fusion reactor aspects Chernitskiy, S.V. Moiseenko, V.E. Tritium breeding calculation in a stellarator blanket Вопросы атомной науки и техники |
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In current blanket projects, tritium breeding ratio (TBR), the ratio of tritium production rate to the neutron production rate, is low (1.1…1.2). The MCNPX Monte-Carlo code has been used to model the neutron kinetics and to look for a principal possibility of increase TBR within a stellarator blanket limited space. |
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Article |
| author |
Chernitskiy, S.V. Moiseenko, V.E. |
| author_facet |
Chernitskiy, S.V. Moiseenko, V.E. |
| author_sort |
Chernitskiy, S.V. |
| title |
Tritium breeding calculation in a stellarator blanket |
| title_short |
Tritium breeding calculation in a stellarator blanket |
| title_full |
Tritium breeding calculation in a stellarator blanket |
| title_fullStr |
Tritium breeding calculation in a stellarator blanket |
| title_full_unstemmed |
Tritium breeding calculation in a stellarator blanket |
| title_sort |
tritium breeding calculation in a stellarator blanket |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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2019 |
| topic_facet |
ITER and fusion reactor aspects |
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https://nasplib.isofts.kiev.ua/handle/123456789/194586 |
| citation_txt |
Tritium breeding calculation in a stellarator blanket / S.V. Chernitskiy, V.E. Moiseenko // Problems of atomic science and technology. — 2019. — № 1. — С. 49-52. — Бібліогр.: 7 назв. — англ. |
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Вопросы атомной науки и техники |
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| first_indexed |
2025-11-24T03:06:05Z |
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2025-11-24T03:06:05Z |
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1849639374194475008 |
| fulltext |
ISSN 1562-6016. ВАНТ. 2019. №1(119)
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2019, № 1. Series: Plasma Physics (25), p. 49-52. 49
TRITIUM BREEDING CALCULATION IN A STELLARATOR BLANKET
S.V. Chernitskiy, V. E. Moiseenko
National Science Center “Kharkov Institute of Physics and Technology”, Kharkiv, Ukraine
In current blanket projects, tritium breeding ratio (TBR), the ratio of tritium production rate to the neutron
production rate, is low (1.1…1.2). The MCNPX Monte-Carlo code has been used to model the neutron kinetics and
to look for a principal possibility of increase TBR within a stellarator blanket limited space.
PACS: 52.55.Hc
INTRODUCTION
Thermonuclear reactions are nuclear reactions
between light atomic nuclei occurring at very high
temperatures (~ 10
8
K and higher). Examples of
thermonuclear reactions are:
D + D = 3He (0.82 MeV) + n (2.45 MeV); Q=3.25 MeV , (1)
D + D = T (1.01 MeV) + p (3.03 MeV); Q=4.04 MeV , (2)
D + T = 4He (3.52 MeV) + n (14.06 MeV); Q=17.6 MeV. (3)
The cross sections of these reactions (and the
probability of interaction of the reacting components)
with an incident energy of less than 1 MeV are 0.09,
0.16, and 5 barn, respectively. The reaction of nuclear
fusion of tritium and deuterium is the most promising
for the implementation in the controlled thermonuclear
fusion, since it requires lower energy of the reagents and
its cross section even at low energies is large enough.
The disadvantages D-T fuel are as follows:
1) tritium is not found in nature and must be
produced of lithium in a blanket of a fusion reactor in
the following nuclear reactions:
6
Li(n,α)T+4.8 MeV,
7
Li(n,n’α)T-2.4 MeV [1];
2) tritium is radioactive [2] (half-life is12.3 years),
system of D-T reactor contains from 10 to 100 kg of
tritium;
3) 80 % of the energy in a D-T reaction is carried
by 14 MeV neutrons, which induce artificial
radioactivity in reactor components and produce
radiation damage.
As a rule, the blanket should not build up the
components of nuclear fuel. However, if tritium is one
of the components of the fuel, then the blanket should
produce it, i.e. besides energy production, to perform
the function of a breeder reactor.
A thermonuclear reactor is usually surrounded by a
shell (blanket) in which the transformation of the energy
of nuclear fusion products into thermal energy is carried
on. In addition to the "passive" blanket providing
radiation protection, there is also an "active" blanket, in
which tritium is produced. The function of the blanket is
to take off energy, transform it into heat for further
transfer it to the electrical generating systems, as well as
protect humans and the environment from ionizing
radiation generated by a fusion reactor. Behind the
blanket in a thermonuclear reactor there is a layer of
radiation protection, the functions of which are to
further weaken the neutron flux and γ-radiation which is
generated owing to the artificial radioactivity to reduce
heat deposition to the cryogenic magnetic coils of the
fusion reactor. Then the biological protection comes
which can be made of concrete with a thickness of about
2 m. The thickness of the blanket and protection layer in
the reactor should be as small as possible especially in
case of stellarator-reactor. At the same time, it is
necessary to provide the reproduction of tritium and the
conversion of the energy of neutrons into heat. In
addition, when using superconducting magnetic coils, it
is necessary to ensure at an acceptable level of damage
to the material of the superconductor, as well as nuclear
heat release in the windings.
At the facility W-7X [3], it is planned to produce
tritium in a blanket with thickness of 50 cm. The limit
value of the tritium breeding ratio (TBR) is planned at
the level of 1.2. However, taking into account technical
issues (20…30 % of the external surface of the blanket
will serve for input windows for different diagnostics)
during operation this value may be lower.
Thus, the purpose of this work is to investigate
possibilities of producing tritium in sufficient quantities
in the blanket of a fusion reactor (especially of a
stellarator).
CONCEPT OF STELLARATOR
BLANKET
When using a deuterium-tritium fusion reactor, it is
necessary to replenish the amount of fuel (D + T) in the
reactor and remove
4
He from the plasma. As a result of
reactions in plasma, tritium burns out, and the main part
of the fusion energy is transferred to neutrons, for which
the plasma is transparent. This leads to the necessity of
placing a special zone (blanket) between the plasma and
the magnetic system, in which tritium is reproduced and
the main part of the neutron energy is absorbed. It
reproduces plasma tritium substitutes burned out.
Tritium can be produced by irradiating lithium-6
with neutron fluxes from the same reactor that the
fusion reaction is carried out:
6
Li+n→(4)He+3T+4.78 MeV. (4)
In this case, not only tritium is formed, but energy
is also released. If the fusion chamber is surrounded by
a layer of
6
Li (it constitutes 7% in the natural lithium), it
is possible to reproduce the consumable tritium. And
although in practice some neutrons are inevitably lost,
their loss is easily replenished by introducing into the
blanket neutron multipliers such as beryllium or lead,
the nuclei of which, when a single fast neutron enters it,
emits two.
Depending on the material of the blanket, a fusion
reactor with D-T fuel can be “pure” or hybrid. The
blanket of a “pure” thermonuclear reactor contains Li,
in which, under the action of thermonuclear neutrons,
50 ISSN 1562-6016. ВАНТ. 2019. 1(119)
tritium is obtained and the thermonuclear reaction is
enhanced from 17.6 to 22.4 MeV. In the blanket of a
hybrid (“active”) thermonuclear reactor, not only tritium
is produced, but also there are zones in which a depleted
238
U is placed to produce
239
Pu. The energy efficiency of
a hybrid thermonuclear reactor is about ten times higher
than in a pure thermonuclear reactor due to fission
reactions. At the same time, better absorption of
thermonuclear neutrons is achieved, which increases the
safety of the installation. However, the presence of
fissile radioactive substances creates a radiation
environment close to that which exists in nuclear fission
reactors.
a
b
Fig. 1. Model of the stellarator reactor:
a – toroidal cross-section; b – poloidal cross-section
With the computer code MCNPX [4], calculations
were performed on the tritium production for different
configurations of the blanket in the stellarator. The
general view of the stellarator model is shown in Fig. 1.
As can be seen from Fig. 1, the model is of the
stellarator of an installation of industrial size.
MODEL 1
Fig. 2 shows the radial structure of the model of a
fusion reactor blanket. It can be seen that a plasma D-T
source of thermonuclear neutrons is located in a vacuum
chamber with a diameter of 3 m. The diameter of the
plasma – 2 m. For the first wall a thickness of 3 cm was
chosen. The first wall in the model is made of HT-9
steel with a mass density of 7.7 g/cm
3
[5].
The thickness of the blanket was chosen 50 cm.
This thickness is chosen for reasons of compactness of
the stellarator installation (the total thickness of the
blanket, reflector and protection should be at the level of
1 m). Blanket is filled with lithium [6]. Outside of the
blanket is a layer of reflector of lead and bismuth
eutectics, the thickness of which is selected 15 cm. The
LBE was assumed to be a mixture of 44.5 wt.% lead
and 55.5 wt.% bismuth with mass density 10.17 g/cm
3
[7].
Fig. 2. Radial structure of the model 1
CALCULATION RESULTS FOR MODEL 1
In the first model, the blanket was filled with
lithium. Concentration of lithium-6 is varied in
calculations. The main result of the calculations is the
tritium breeding ratio (TBR) – the ratio of the number of
produced tritons to the number of spent (lost) neutrons.
The results of calculations for the production of tritium
are presented in Fig. 3.
Fig. 3. Tritium breeding ratio as function of lithium
enrichment
It can be seen that the main contribution to the
production of tritium is made by the lithium-6 reaction.
This is explained by the fact that lithium is a light
element and the neutron spectrum in the blanket is low-
energy. This increases the possibility of a neutron
capture reaction with lithium-6 with the formation of
tritium. The maximum TBR for this case is 1.22 and is
observed if the blanket is filled with lithium with
enrichment in lithium-6 to 20 %.
MODEL 2
Fig. 4 shows another arrangement of a fusion reactor
blanket.
1 – vacuum chamber,
2 – first wall,
3 – blanket,
4 – radial reflector
(LBE)
ISSN 1562-6016. ВАНТ. 2019. №1(119) 51
Fig. 4. Radial structure of the model 2.
1 – vacuum chamber; 2 – first wall; 3 – LBE coolant;
4 – lithium; 5 – radial reflector (LBE)
Unlike the first model, here between the first wall
and the blanket is a layer of lead and bismuth eutectic
(LBE). Lead acts as an amplifier of a stream of fast
neutrons due to the threshold reaction of neutron
multiplication, such as
208
Pb (n, 2n)
207
Pb. The thickness
of this zone was chosen 15 cm because the mean-free-
path of a fast neutron in LBE is equal to this magnitude.
Fig. 5. Number of neutrons from LBE as function of
radial width of LBE layer
Moreover, as shown by the calculation results
(Fig. 5), the maximum neutron multiplication from 2.5
to 2.7 is obtained when the LBE thickness is in the
range of 15…25 cm. However, taking into account that
the model should be compact, the thickness of this zone
is chosen minimal (15 cm).
CALCULATION RESULTS FOR MODEL 2
In this model, as in the previous case, the blanket
was filled with lithium with different concentrations of
lithium-6. The results of calculations for the tritium
production are presented on Fig. 6. It can be seen that
the tritium production is due to the neutron capture
reaction on lithium-6, while lithium-7 does not make a
noticeable contribution. This is because the neutron
spectrum in the blanket becomes even more low-energy
then in the model 1. The maximum amount of TBR is
1.34 and is observed if the blanket is filled with lithium
with enrichment in lithium – 6…30 %.
Fig. 6. Tritium breeding ratio as function of lithium
enrichment
MODEL 3
Fig. 7 shows another model of a hybrid
thermonuclear reactor blanket.
Fig. 7. Radial structure of the model 3
In this calculation model, behind the first wall thin
layer (1 cm) of a homogenized mixture of plutonium
with iron is put (Pu 239 – 46.8778 %, Pu 240 –
19.1079 %, Pu 241 – 3.483 %, Pu 242 – 4.2093 %, O 16
– 10 % and Fe – 16.322 %). The isotopical content
reflects the concentration of plutonium isotopes in spent
nuclear fuel of the power plant nuclear reactors. The
thickness of the blanket has decreased and becomes
35 cm.
CALCULATION RESULTS FOR MODEL 3
The results of calculations for the production of
tritium are presented on Fig. 8. The maximum amount
of TBR is 2.9 and is observed when the blanket is filled
with lithium with enrichment in lithium – 6…10 %.
1 – vacuum chamber,
2 – first wall,
3 – coolant (LBE),
4 – blanket,
5 – radial reflector
(LBE)
1 – vacuum chamber,
2 – first wall,
3 – plutonium
4 – blanket,
5 – radial reflector
(LBE)
52 ISSN 1562-6016. ВАНТ. 2019. 1(119)
Fig. 8. Tritium breeding ratio as function of lithium
enrichment
This increase of tritium production can be explained
by the fact that neutron multiplication in the plutonium
layer is more intense than in lead. In addition, the
number of produced secondary neutrons during fission
is 3.1, which is extracted from the calculation results.
CONCLUSIONS
Basing on the calculations it can be concluded that
for first model TBR=1.22. In this case, lithium is
located directly behind the first wall and serves as a
coolant, and for tritium production. For second model
TBR=1.34. Here, behind the first wall lead-bismuth
eutectic is located whose main function is the
multiplication of neutrons. For third model TBR=2.9. In
this calculation model, behind the first wall thin layer of
a homogenized mixture of plutonium with iron is
located. Calculations have shown that the effective
neutron multiplication factor will be at the level of 0.7
(deep subcriticality) and the energy released in a thin
layer will be 258 MeV per neutron source which is more
than one order of magnitude higher than in pure fusion.
To reduce this energy by 5 times, it is necessary to
reduce the amount of plutonium by 2 times. In this case
TBR=1.47. In this instance, we can say that with this
arrangement, the power plant can produce tritium in
sufficient quantities for its own needs.
REFERENCES
1. V.E. Pluschev. Chemistry and technology of rare and
trace elements. Graduate School, 1976.
2. R.V. Osborne. Tritium Hazard Report: Pollution and
Radiation Risk from Canadian Nuclear Facilities //
Canadian Nuclear Association, 2007.
3. F. Warmer, C. D. Beidler, A. Dinklage, et al. From
W7-X to a HELIAS fusion power plant: motivation and
options for an intermediate-step burning-plasma
stellarator // Plasma Physics and Controlled Fusion.
2016, v. 58, № 7, p. 074006.
4. For the U.S. DEPARTMENT OF ENERGY. Monte
Carlo N-Particle Transport Code System for
Multiparticle and High Energy Applications, Version
2.4.0. Los Alamos National Laboratory, Los Alamos
report LA-CP-02-408, 2002.
5. ORNL, Fusion Materials. 1999. http://www.ms.ornl.go
v/programs/fusionmtlspdf/june1999/hashimoto1.pdf.
6. I.R. Kirillov. RF DEMO Team. Lithium cooled
blanket of RF DEMO reactor // Fusion Eng. Des. 2000,
v. 49, 50, p. 457-465.
7. OECD NEA, 2007. http://www.oecd-
nea.org/science/reports/2007/pdf/chapter2.pdf.
Article received 11.01.2019
НАРАБОТКА ТРИТИЯ В СТЕЛЛАРАТОРНОМ БЛАНКЕТЕ
С.В. Черницкий, В.Е. Моисеенко
В текущих проектах коэффициент размножения трития – отношение скорости образования трития к
скорости производства нейтронов, низок, и составляет величину 1,1…1,2. Монте-карловский код MCNPX
использовался для моделирования нейтронной кинетики и демонстрации принципиальной возможности
увеличения наработки трития в пределах ограниченного пространства бланкета стелларатора.
НАПРАЦЮВАННЯ ТРИТІЮ В СТЕЛАРАТОРНОМУ БЛАНКЕТІ
С.В. Чернiцький, В.Є. Моісеєнко
У поточних проектах коефіцієнт розмноження тритію – відношення швидкості утворення тритію до
швидкості виробництва нейтронів, низький, і становить величину 1,1…1,2. Монте-карлівcький код MCNPX
використовувався для моделювання нейтронної кінетики і демонстрації принципової можливості
збільшення напрацювання тритію в межах обмеженого простору бланкету стеларатора.
http://www.ms.ornl.gov/programs/fusionmtlspdf/june1999/hashimoto1.pdf
http://www.ms.ornl.gov/programs/fusionmtlspdf/june1999/hashimoto1.pdf
|